Flexible with single door strap. Designed for use on wood-frame sliding doors from 1-1/2" to 2" thick. Slot in top of door strap allows lateral and vertical adjustment. 450 pound capacity per pair. Packed with two end caps and bolts for attaching door strap. Made of durable one-piece, precision-formed steel and has self-lubricating Delrin bearings. Boxed.